New Methods for Characterizing North Sea Reservoirs with Multi-frequency Dielectric Measurements

Transcription

1 1 New Methods for Characterizing North Sea Reservoirs with Multi-frequency Dielectric Measurements Jim White Schlumberger Aberdeen Thanks also to David Dangfa, Harish Datir

2 Outline 2 Dielectric physics and interpretation Dielectric Scanner tool Field examples Saturation in formation with variable water salinity Texture analysis (measuring m in Archie Equation) West of Shetland exploration well Block 9 Northern North Sea: Measure Sw in reservoir with no water zone. Conclusions

3 Physics Three Origins of Dielectric Permittivity ) Electronic Polarization H 2 O ) Oriented Polar molecules - 3) Interface on surfaces

4 Dielectric Physics Polarization Type Mechanism E = 0 E > 0 ε r value 4 Electronic (All nucleii) Oil ~ 2 Rock ~ 5-8 Electronic polarization Orientational (Water molecule) Water ~ Molecular orientation Interfacial (Rock texture)~ Textural Effect Interfacial polarization 1e+5 1e+6 1e+7 1e+8 1e+9 1e+10 (Hz) Frequency

5 Dielectric Dispersion as function of frequency 5 Permitiv Permittivi vity Dielectric Scanner measures 4 different frequencies 10 8 Fre que ncy, Hz 10 9 Frequency, Hz Ca Rock rbona 1 te 1 Ca Rock rbona 2 te 2 CRI Textural information ( m exponent in Archie) Water content information

6 Processing Flow 6 Acquisition: -296 raw signals (Phase and Attenuation) Geometrical deliverables: - Permittivities - Conductivities (at 4 frequencies) Petrophysical Deliverables - Water volume - Water Conductivity - Variable m, CEC *SPWLA 2006 Textural model*, simplifying to the Complex Refractive Index method (CRIM) at high frequencies.

7 Processing Flow 7 Acquisition: -296 raw signals (Phase and Attenuation) Geometrical deliverables: - Permittivities - Conductivities (at 4 frequencies) Petrophysical Deliverables - Water volume - Water Conductivity - Variable m, CEC From dielectric From other measurements Water volume Total porosity = Water saturation (Sw or Sxo)

8 Outline 8 Dielectric physics and interpretation Dielectric Scanner tool Field examples Saturation in formation with variable water salinity Texture analysis (measuring m in Archie Equation) West of Shetland exploration well Block 9 Northern North Sea: Measure Sw in reservoir with no water zone. Conclusions

9 The Dielectric Scanner 9 Length 11.3 feet, and fully combinable Fully articulated pad Vertical resolution 1 inch Depth of investigation: ~ 1 to 4 inch Maximum logging speed: 3600 ft/hr

10 Outline 10 Dielectric physics and interpretation Dielectric Scanner tool Field examples Saturation in formation with variable water salinity Texture analysis (measuring m in Archie Equation) West of Shetland exploration well Block 9 Northern North Sea: Measure Sw in reservoir with no water zone. Conclusions

11 Variable Formation Water Salinity 11 Standard logs SP GR Micro-Resistivity X-plot Porosity 50 0 Neutron Porosity 50 0 Caliper 6 16 X100 Deep Resistivity Resistivity Density Porosity 50 0 Porosity Moved Oil? High deep resistivity and high porosity Invasion from shallow resitivity X200 X300 X400 Oil (immovable?) X500 X600 Water zone X700 SPE X800

12 Variable Formation Water Salinity Dielectric-Scanner real time answer Salinity 0 30 SP GR Caliper 6 16 Oil 0 Sw 1 Micro-Resistivity Deep Resistivity Dielectric Scanner Water porosity Hydrocarbon 12 DS Water Porosity 50 0 X-plot Porosity 50 0 X100 Fresh Water Dielectric porosity overlays with total porosity Low mobility oil X200 X300 X400 X500 X600 Water zone X700 X800

13 Outline 13 Dielectric physics and interpretation Dielectric Scanner tool Field examples Saturation in formation with variable water salinity Texture analysis (measuring m in Archie Equation) West of Shetland exploration well Block 9 Northern North Sea: Measure Sw in reservoir with no water zone. Conclusions

14 Carbonate Texture Analysis in water zone 14 Standard logs in a carbonate reservoir Clean water zone? Porosity p.u. SP GR Caliper 6 16 Sxo 0 1 Sw 0 1 Sw XX00 Micro-Resistivity Deep Resistivity Resistivity X-plot Porosity 50 0 Neutron Porosity 50 0 Density Porosity 50 0 Porosity XX10 XX20 XX30 Sw= 60%, not 100% Computed using Archie m=2 XX40 XX50 XX60 Unexpectedly high resistivity zone with good porosity SPE XX70

15 Carbonate Texture Analysis in water zone 15 Wellsite interpretation Compare dielectric porosity with total porosity. Salinity 0 50 SP GR Caliper 6 16 HC 0 Sw Diel. 1 Sw XX00 XX10 Micro-Resistivity Deep Resistivity Resistivity Hydrocarbon Dielectric water porosity 50 0 X-plot Porosity 50 0 Porosity XX20 High resistivity likely caused by change in rock texture - not from hydrocarbon! XX30 Dielectric Porosity and total porosity overlay. XX40 XX50 XX60 XX70

16 Carbonate Texture Analysis in water zone 16 SP Hydrocarbon Confirm rock texture change by looking at measured m curve. Salinity 0 50 GR Caliper 6 16 HC 0 Sw Diel. 1 XX00 Micro-Resistivity Deep Resistivity Dielectric water porosity 50 0 X-plot Porosity 50 0 XX10 XX20 XX30 m measured from dielectric (Varies from 1.9 to 2.8) XX40 XX50 XX60 XX70

17 Outline 17 Dielectric physics and interpretation Dielectric Scanner tool Field examples Saturation in formation with variable water salinity Texture analysis (measuring m in Archie Equation) West of Shetland exploration well Block 9 Northern North Sea: Measure Sw in reservoir with no water zone. Conclusions

18 Gamma ray Resistivity Density Neutron Exploration well West of Shetlands Triple combo logs Water based mud No separation Anomalous response - is hydrocarbon present? Deep/shallow resistivity separation indicates mobile hydrocarbon

19 Gamma ray Resistivity Density Neutron Formation Testing Pressure Mobility No successful tests in time available (all tight )

20 Gamma ray Resistivity Density Neutron Magnetic Resonance Poro sity T1 T1 T Porosity.3 0 Low viscosity oil from MR Low dielectric porosity confirms that hydrocarbon is present in upper zone Density porosity Dielectric porosity

21 Outline 21 Dielectric physics and interpretation Dielectric Scanner tool Field examples Saturation in formation with variable water salinity Texture analysis (measuring m in Archie Equation) West of Shetland exploration well Block 9 Northern North Sea: Measure Sw in reservoir with no water zone. Conclusions

22 Gamma ray Resistivity Density Neutron Porosity Dielectric T1 1.5 shell Magnetic Resonance Block 9 Northern North Sea T1 2.7 shell T1 4 shell Heavy oil zone drilled with Oil Based Mud No water zone How to determine oil-in-place with no Rw?

23 Water Saturation 0 1 Gamma ray Resistivity Density Neutron Porosity Dielectric & Density T1 1.5 shell Magnetic Resonance T1 2.7 shell T1 4 shell Sw = Dielectric Porosity Density Porosity Water salinity is also measured...

24 Water Saturation Salinity Gamma kppmray Resistivity Density Neutron Porosity Dielectric & Density T1 1.5 shell Magnetic Resonance T1 2.7 shell T1 4 shell Water salinity = 40kppm Water salinity is also measured...

25 Water Salinity kppm Resistivity Density Neutron Porosity Dielectric & Density T1 1.5 shell Magnetic Resonance T1 2.7 shell T1 4 shell Water salinity = 40kppm Note it is not possible to determine water volume from MR BFV because of interference from heavy oil signal.

26 Water Salinity kppm Resistivity Density Neutron Porosity Dielectric & Density T1 1.5 shell Magnetic Resonance T1 2.7 shell T1 4 shell Dielectric measurements can give reliable Sw and salinity measurements in hydrocarbon zones drilled with OBM, Even where no water zone has been found!

27 Summary Dielectric dispersion helps measure: 27 Residual oil saturation in reservoirs drilled with WBM, even with unknown or varying salinity. Formation saturation (Sw) in hydrocarbon zones drilled with OBM (No requirement for water zone or a resistivity measurement.) Thin beds properties beds down to 1 Texture analysis m cementation exponent in water based muds

28 Conclusions 28 In increasingly complex reservoirs, Dielectric Dispersion will become a valuable tool to help predict reservoir performance and estimate reserves.

29 Conclusions 29

30 Conclusions 30